This revised application is renewed for two reasons: 1) some research-plans previously proposed have been completed while awaiting the decision, consequently the research on the cat was deleted; 2) the understanding of the proposed field has shown remarkable progress, particularly in the superior colliculus, consequently the significance of this study has been greatly reinforced by application of new techniques and information. It is proposed to interpret the problems in relation to visual perception during eye movements in neurophysiological terms by recording single units in the visual cortex and the thalamus of alert monkeys. In connection with the ability of the brain to distinguish between an image motion produced by eye-movement and object-movement, the neuronal mechanisms subserving the corollary discharge hypothesis will be investigated. Suppose a corollary discharge existed, a cell would be coded with temporal information about an impending eye movement. Some cells would be coded specifically with a direction, amplitude or speed of eye movement or instantaneous position of the eyes. Thus, the cellular activity, response characteristics or even receptive field organization could be modified during eye movements. Keeping these assumptions in mind, the unit activity will be correlated with temporal relation to eye movement and spatial relation to eye position. Furthermore, the relations will be evaluated quantitatively between the effect of corollary discharge and the size of the impending eye movement by controlling the parameters of eye movement and stimulus movement independently.